Device for producing electric pulses, particularly for medical purposes



March 25, 1952 F. SCHUHFRIED 2,590,216

DEVICE FOR PRODUCING ELECTRIC PULSES, PARTICULARLY FOR MEDICAL PURPOSES FiledJan. 21. 1949 IN V EN TOR.

Patented Mar. 25, 1952 DEVICE FOR PRODUCING ELECTRIC PULSES, PARTICULARLY FOR MEDICAL PURPOSES Felix Schuhfried Vienna, Austria Application January 21, 1949, Serial No. 71,968 In Austria June 30, 1948 13 Claims. (01. 128-422) The present invention relates to a device for producing electrical pulses, particularly for purposes of medical therapy, such as, for instance, the treatment of paralysis, or for purposes of diagnostic, e. g., to determine the electrical excitability of a patient.

The invention contemplates to provide a. de-' vice for producing electrical pulses for purposes,

of.medical therapy and/or diagnostic which is adaptable to varying requirements and which in spite of a relatively simple construction will enable not only the attending physician but also the patient himself to make the adjustments news I sary for obtaining electrical pulses of such kind as will be best to suit the requirements in each particular field of application. Accordingly it is an I object of the invention to make possible the production of pulses the duration of which is controllable and whose intervals and curve slope, i. a, rise time, are adjustable.

' A further object of the invention is to provide a device for producing electrical pulses for the purposes above indicated wherein a change of the adjustment of the duration of the pulses will bring about separate manipulation-for that latter change.

A further object of the invention is to provide a device of the kind referred to which is capable of producing electrical pulses in periodical sequence as well as individual pulses, a key or the like being provided for the latter purpose.

. A further object of the invention is to provide a device of the kind referred to enabling the patient, even if bedridden, to bring into play, such asby pressing akey, electricalpulses whoserise time has been previously adjusted by the physician.

Still a further object of the invention is to provide a device of the kind referred to wherein the amplitude of the electric pulses can be controlled by the patient himself so that the intensity of these pulses will increase decrease as desired. Finally, it is an object of the invention to provide a device of the kind referred to having means for automatically increasing and. decreasing the amplitude of the pulses.

Other objects of the invention will appear-as the description proceeds, reference being had to 50 Fig. 1 shows by way of example a circuit diathe accompanying drawing, in which:

gram of an embodiment of the invention;

Fig. 2 illustates a modification of a portionoi the circuit of Fig. 1; and I 3 shows another modification.

an approximately proportionalv change of the rise time without requiring any by changing the slope of the pulse curve. "the same purpose there may be used an Rich-etwork (resistor-inductance network) instead of an tode is used so that a disturbing reaction of the output circuit on the operation of the multivie bra-tor is avoided. As conventional, the plate of the tube B1 is connected across a condenser C1 to the control grid of the tube B2 which in turn is connected to the cathode of this tube B2 across aresistor R1. The screen grid of the tube B2 is included into the multivibrator circuit by being connected through the condenser C2 with the grid of the tube E1; the coordinated grid leak being indicated at Rs. Since the mode of operation of a multivibrator is well known to those skilled in the art no detailed description thereof is deemed Due to the alternating blocking of the two tubes according to the multivibrator principle there is created at" the plate resistor RA of the pentode B2 a periodical series of pulses whose duration or width is determined substantially by the time constant T1=R1.C1 whereas for the interval between the pulses the time constant T2=R2.C2 is determinative. Due to the electronic coupling of the output circuit with the multivibrator circuit proper through the intermediary of the pentode B2 a disturbing reaction of the output circuit upon the shape of the pulses, the pulse duration and the interval between the pulses of develop at the resistor RA are suppliedby means of a voltage divider comprising resistors R5 and R5 to a time-constant network comprising a resistor R3 and a condenser C3. The condenser C3 is arranged betweenthe grid and the cathode of an output tube 133 in whose plate circuit there are arranged electrodes E to be applied to the patient for purposes of diagnosis or for therapeutical treatment. It will be obvious to those skilled in the art that the electrodes E may be shunted by a current limiting device, e. g. a resistor (not shown) to limit the current passing through the body of the patient. The time-constant network B3, C3 causes a change of the shape of the pulses For RC network (resistor--capacitance network).

According to the invention the time constants variable in order to be able to adjust the pulse duration. (tl'irough T1). the duration of the intervalshetween the. pulses (through T2) and the 3 slope of the pulse rise (through T3) to suit the medical requirements of each particular case. The variability of the time constants may be made possible by making either the condensers C1, C2, C3 or the resistors R1, R2, R3 or both the condensers and the resistors either continuously variable or switchable from one value to another. It has been found most suitable to make the CH."

pacitances switchable and the resistors contin-v uously variable. In the example shown, the resistors R1, and R3 are indicate-:1 by arrows to be variable resistors.

, tact in parallel thereto may be placed in the Another possibility for the control of the slope of the pulses is indicated in Fig. 2. In order to avoid possible distortions through the setting-in of grid current and a counter potential occasioned thereby at certain values of R3, the latter is made constant and a variable resistor R4 is arranged between the grid and the cathode of the tube B3, which variable resistor R4 is in series with the condenser C3.

For the medical application of the device it is important that with a variation of the pulse duration there goes a simultaneous regulation of the rise time of the pulse. To achieve this, the adjusting element which controls the time constant T1 determining the duration of the pulses is mechanically coupled with the adjusting element for the time constant T3 which determines the rise time of the pulses. Fig. 1 shows for that purpose in parallel'to the variable resistor R3 a further variable resistor R3" which. as indicated by a dotted line, is mechanically coupled with the variable resistor R1. Thus the time constant T3 is determined by the resistance resulting from the'parallel connection of the resistors R3 and R3, and by the capacitance C3. With this arrangement the time constant T3 which determines the rise time varies in the same sense as the time constant T1 which determines the pulse duration. It is also possible to leave out the resistor R3 and to provide mechanical coupling between the variable resistors R1 and R3.

The variable resistor R4 shown in Fig. 2 is to be understood as being coupled with the variable resistor R1 of Fig. 1,

The invention further contemplates to adapt the described device for the generation of individual pulses. For that purpose the multivibrator is transformed into an electronic switch by interrupting the feed-back from the second tube B2 to the first tube B1 and by a suitable voltage control of the first tube B1. To interrupt the feedback there is provided in Fig. l a switch S2, which separates the coupling condensor C2 from the screen grid of the tube B2. Simultaneously with the switch S2, the switch S1 is closed in order to supply across the resistor R7 a blocking negative bias to the grid of the tube B1. If now, by closing of the switch S3, a positive voltage derived from the voltage divider Ra, R9 is applied to the grid of the tube B; so that this tube becomes conductive and draws current, a voltage pulse is transmitted through the time-constant network C1, R1 to the control grid of the pentode B2, the duration of the pulse being determined by the time-constant T1:R1 C1 and being adjustable in the manner previously described. Due to the already mentioned mechanical coupling of the adjusting elements for the time constants T1 and T3, the rise time of the pulses may be influenced simultaneously with the duration of the "pulses.

Forthe medical applicability'it isimportant switch case mentioned or there may be provided suitable actuating contacts at other points of the circuit. According to Fig. 1 there is provided in the patients switch case P a switch S4 which enables the release of individual pulses of variable rise time. Prior to the actuation of the switch S4 the multivibrator is cut out by applying to the control grid of the tube B1 a blocking negative voltage by means of the switch S1. Then a positive voltage derived from the voltage di vider R11, R9 can be applied by means of the switch S4 to the time constant network R3, C3 which, in the manner described above, causes a voltage pulse in the circuit including the patient which pulse may be adjusted through adjustment of the time constant T3.- In the patients switch case P there is further provided a variable resistor R10 for adjusting the amplitude of the individual pulses or of the periodic output pulses of the multivibrator so that the patient himself may select the intensity of the impulses and, in particular, make this intensity rise and fall. The variable resistor R111 may be connected, e. g., into the screen grid circuit of the pentode Ba.

Automatic increase and decrease of the intensity of the pulses may be obtained by applying to the screen grid of the pentode B: an alternating voltage which controls the amplification, which voltage may be derived from a second multivibrator and effects a modulation of the output pulses. Such an arrangement is shown in Fig. 2 according to which the screen grid of the tube B3 is connected across a resistor R11 and the secondary of a transformer T to the positive terminal of the voltage source. To the primary of the transformer T there is applied the modulating alternating voltage. Screen grid modulation may also be obtained in the manner shown in Fig. 3 by connecting the screen grid of tube B; with the plate of another tube 134 whose grid is supplied with a control voltage having the desired modulating frequency.

To those skilled in the art, it will be obvious that various changes may be made in the details of the circuit without departing fromthe spirit of the invention. For example, the time constant network T3 might be arranged in parallel to the electrodes E, as is shown in Fig. 3.

In order to be able to apply direct current to the patient, there may be provided a switch S5 across which the grid of the tube B2 obtains a negative bias, whereby this tube is blocked and tube B3 becomes conductive.

What I claim is: I

1. A device for producing electrical pulses for purposes of medical therapy and/or diagnostic, comprising, in combination, a multivibrator circuit having two thermionic tubes each including a cathode, a plate and at least one grid therebetween. -said two thermionic tubes being interconnected by a first time-constant network for controlling the duration of the pulses,- by a secand time-constant network for controlling the intervals between the pulses, of which said two time-constant networks one at least is variable, and also by a third time-constant network adapted to receive the output pulses of the multivibrator and being-variable for controlling the rise time (slope of the'curve) of the output pulses, and means for connecting the output of said multivibrator circuit to two electrodes adapted to be applied to the body of the patient. 1

2. A device for producing electrical puhes for purposes of medical therapy and/or diagnostic, comprising, in combination, a multivibrator circuit having two thermionic tubes each including a cathode, a plate and at least one grid therebetween, said two thermionic tubes being interconnected by a variable first time-constant network for controlling the duration of the pulses, by a second time-constant network -for controlling the intervals between the pulses, and also by a third time-constant network adapted to receive pulses ismechanically coupled:wi.th a-variable resistor for varying the Pulses.

rise time of the output 4; A device for producing electrical pulses for purposes of medical therapyand/or diagnostic, comprising, in combination, multivibrator ciricuit having two thermionic tubes eachincluding a cathode, a plate and; at least one grid therebetween, said two thermionic tubes being interconnected by a first time-constant network for controlling the duration of the pulses, by a second time-constant network for controlling the intervals between the pulses, of which said two time-constant networks one at least is variable, and also by a third time-constant network adaptedto receive the output pulses of the multi vibratonand being variable for controlling the rise time of the output pulses, an electron tube having-acathode, plate and at least a control grid in addition to said two tubes of the multivibrator, said third network including a resistance inseries with. a capacitor, the latterbeingi 5. A device for producing electrical pulses for purposes of medical therapy and/or diagnostic, comprising, in combinatioina multivibrator circuit having two thermionic tubes each including a cathode, a plate and at'least one grid there- 'between, said two thermionic tubes being inter connected by'a first time constant network having atleast one variable element for controlling least a control grid in addition to said two tubes of the multivibrator, said third networkfor controlling the rise time of the output pulses including a resistance in series with a capacitor, said {resistance comprising two resistors in parallel of which one at least is variable and mechanically coupled with said variable element of said first network for controlling the duration of the pulses, and said capacitor being arranged between said control grid and said cathode of said additional electron tube, and means for connecting the output of said multivibrator to electrodes adapted to be applied to the body of the patient.

6. A device for producing electrical pulses for purposes of medical therapy and/or diagnostic, comprising, in combination, a multivibrator cir cuit having two thermionic tubes each including a cathode, a plate and at least one grid there- I between, said two thermionic tubes being interconnected by a first time-constant network including a variable resistor for controlling the duration of the pulses, by a second time-constant network including a variable resistor for controlling the intervals between the pulses, and

also by a third time-constant network adapted to receive the output pulses of the multivibrator and being variable for controlling the rise time of the pulses, an electron tube having a cathode, a plate and at least a control grid in addition to said two tubes of the multivibrator, said third time-constant network for controlling the rise time of the pulses comprising the series connection of a resistor and an. impedance, said impedance being connected between said grid and said cathode of said additional electron tube and containing a condenser and a variable resistor,

the latter being mechanically coupled with'said variable resistor of said first time-constant network controlling the duration of the pulses, and means for connecting the output of said multivibrator to electrodes adapted to be applied to the body of the patient.

the duration of the pulses, by a second timeconstant network for controlling the intervals between the pulses, and also by a third time- 7. A device for producing electrical pulses for purposes of medical therapy and/or diagnostic,

comprising in combination, a multivibrator circuit having two thermionic tubes each including a cathode, a plate and at least one grid therebetween, said two thermionic tubes being interconnected oy a first time-constant network for controlling the duration of the pulses, by a second time-constant network for controlling the intervals: between the pulses and also by a third "time-constant network adapted to receive the "output pulses of the multivibrator and being variable for controlling the rise time of thefoutput pulses, and twoelectrodes adapted to be applied to the body of thepatie'nt, said third timeconstant network for-controlling the risetime b'etwecn, said two thermionic tubes being interconnected by a variable first time-constant network for controlling the duration of the pulses, by a variable second time-constant network for controlling the intervals between the pulses, and also by a third time-constant network adapted to receive the output pulses of the multivibrator and being variable for controlling the rise for controlling the rise time of the output pulses,

an electron tube having a cathode, a plate and at are of the output pulses, means for transform- 7 switch circuit comprising two switches, one of said two switches being adapted to interrupt the feedback from said second tube to said first tube and the other of said two switches being adapted to apply a cut-off voltage to the grid of said first tube, means for actuating the electronic switch to release individualpulses whose duration and rise time are adjustable by means of said first and third time-constant network comprising a switch so connected into the circuit as to apply a positive voltage to the grid of said first tube and means for connecting the output of said multivibrator to electrodes adapted to be applied to the body of the patient.

9. A device for producing electrical pulses for purposes of medical therapyl and/or diagnostic, comprising, in combination, a. multivibrator circuit having a first and a second thermionic tube, each including a cathode, aplate and at least one grid therebetween, said two thermionic tubes being interconnected by a variable first timeconstant network for controlling the duration of the pulses, by a variable second time-constant network for controlling the intervals between the pulses, and also by a third time-constant.

network adapted to receive the output pulses of the multivibrator and being variable for controlling the rise time of the output pulses, means for releasing individual pulses including two switches of which one is adapted to apply a negative cut oil potential to the control grid of said first tube and the other switch is adapted to transmit a voltage pulse to said third timeconstant network, and means for connecting the output of said multivibrator to electrodes adapted to be applied to the body of the patient.

10. A device for producing electrical pulses for purposes of medical therapy and/or diagnostic, comprising, in combination, amultivibrator circuit having two thermionic tubes each including a cathode, a plate and at least one grid there between, said two thermionic tubes being interconnected by a variable first time-constant network for controlling the duration of the pulses, by a variable second time-constant network for controlling the intervals between the pulses of which said two time-constant networks one at least is variable, and also by a third time-constant net work adapted to receive the output pulses of the multivibrator and variable for controlling the rise time of said output pulses, means for controlling the amplitude of said output pulses, and means for connecting the output of said multivibrator to electrodes adapted to be applied to the body of the patient.

11. A device for producing electrical pulses for purposes of medical therapy and/or diagnostic,

-comprising, in combination, a multivibrator circuit having a first and a second thermionic tube, each including a cathode, a plate and at least one grid therebetween, said two thermionic tubes being interconnected by a variable first time-constant network for controlling the duration of the pulses, by a variable second time-constant network for controlling the intervals between the pulses and also by a third time-constant network adapted to receive the output pulses of the multivibrator and being variable for controlling the rise time'of the output pulses, means for transforming the multivibrator circuit into an electronic switch circuit comprising two switches, one of said two switches being adapted to interrupt the feedback from said second tube to said first jtubeand the other of said two switches being adapted to apply a cut-off voltage to the grid of said first tube, means for actuating the electronic switch to release individual pulses whose duration and rise time are adjustable by means of said first and third time-constant networks, comprising a switch so connected into the circuit as to apply a positive voltage to the grid of said first tube, means for controlling the amplitude of said output pulses, and means for connecting the output of said multivibrator to electrodes adapted to-be applied to the body of the patient, said means for releasing individual pulses and said means for controlling the amplitude thereof being situated in a switch case arranged so as to be easily operable by the patient; 9

12. A device as claimed in claim 1, having mean for modulating the output pulses.

13. A device for producing electrical pulses for purposes of medical therapy and/or diagnostic, comprising, in combination, a multivibrator circuit having two thermionic tubes each including a cathode, a plate and at least one grid therebetween, said two thermionic tubes being interconected by a variable first time-constant network for controlling the duration of the pulses, by a variable second time-constant network for controlling the intervals between the pulses and also by a third time-constant network adapted to receive the output pulses of the multivibrator and being variable for controlling the rise time of the output pulses, an electron tube in addition to said two tubes of the multivibrator, said additional electron tube having a cathode, a plate, and at least a control grid and a screen grid between said cathode and plate, means for modulating said output pulses including a transformer whose primary is adapted to be connected to a source of alternating modulating voltage and whose secondary is connected into the screen grid-plate circuit of said additional tube, and means for connecting the output of said multivibrator to electrodes adapted to be applied to the body of the patient.

FELIX SCHUHFRIED.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Great Britain Nov. 12, 1936 

